#include <bits/stdc++.h>

#define f first
#define s second
#define pb push_back
#define mp make_pair

using namespace std;

typedef long long ll;
typedef pair<int, int> pii;
typedef pair<long long, long long> pll;

const int N = 300500, inf = 1e9, mod = 998244353;
const ll INF = 1e18;

int sum(int a, int b) {
    a += b;
    if (a >= mod)
        a -= mod;
    return a;
}

int sub(int a, int b) {
    a -= b;
    if (a < 0)
        a += mod;
    return a;
}

int mult(int a, int b) {
    return 1ll * a * b % mod;
}

int bp(int a, int b) {
    int res = 1;
    while (b) {
        if (b & 1)
            res = mult(res, a);
        a = mult(a, a);
        b >>= 1;
    }
    return res;
}

int inv(int x) {
    return bp(x, mod - 2);
}

int n;
bool was[N];
ll a[N], b[N];
ll A, B;

void solve() {
    cin >> n;


    for (int i = 0; i < n; i++) {
        cin >> a[i] >> b[i];
        A += a[i];
        B += b[i];
    }
    if (n % 2 == 1 || A % (n / 2) != 0 || B % (n / 2) != 0) {
        cout << "impossible\n";
        return;
    }
    A = A / (n / 2);
    B = B / (n / 2);
    set<pair<pll, int> > st;
    for (int i = 0; i < n; i++)
        st.insert({{a[i], b[i]}, i});
    for (int i = 0; i < n; i++) {
        if (was[i])
            continue;
        was[i] = 1;
        st.erase({{a[i], b[i]}, i});
        auto it = st.lower_bound({{A - a[i], B - b[i]}, -1});
        if (it == st.end() || it->f.f != A - a[i] || it->f.s != B - b[i]) {
            cout << "impossible\n";
            return;
        }
        was[it->s] = 1;
        st.erase(it);
    }
    cout << "possible\n";
}

int main() {
#ifdef DEBUG
    freopen("input.txt", "r", stdin);
#endif
    ios_base::sync_with_stdio(false);
    int t = 1;
//    cin >> t;
    for (int i = 1; i <= t; i++) {
//        cout << "Case #" << i << endl;
        solve();
    }
}